Is this acceptable by all C Standards?
for (int i=0; i<n; i++) {
// do stuff
}
Or should I write it like this just to be sure it works everywhere?
int i;
for (i=0; i<n; i++) {
// do stuff
}
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1No. You need to write second one.Aleksandar Makragić– Aleksandar Makragić2016-01-21 18:17:55 +00:00Commented Jan 21, 2016 at 18:17
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There is only one C standard, which is currently ISO 9899:2011. And that accepts this very well. And the second version has different semantics.too honest for this site– too honest for this site2016-01-21 18:46:54 +00:00Commented Jan 21, 2016 at 18:46
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1 Answer
No, it's valid since C99 only. If you want your code to be valid under old standards use
int i;
for (i = 0 ; i < n ; i++)
And also, read this comment by @JoachimPileborg it complements well this answer.
3 Comments
Some programmer dude
It might be worth noting that before C99 the variable need to be declared in the declaration block first in the function as well. One can't simply declare the loop count variable just before the loop (unless the loop is the first non-declaration statement in the function).
too honest for this site
This has different semantics, as the scope of
i is now that of the enclosing block, not just the for loop.
Weather Vane
I sometimes
break from a loop and use the value of i after the loop to see if it completed naturally. But if i has gone out of scope that is not possible.